The invention relates to a fixing device for fixing at least one support arm, in particular a spring arm.
For the purpose of supporting medical apparatus, in hospitals, doctors"" practices and similar establishments supports are used which are suspended on the ceiling of the particular treatment room or operating theatre by way of a support arm which is preferably constructed as a spring arm. This ensures that the floor of the treatment room or operating theatre is always freely accessible and, in particular, easy to clean and to disinfect, so that the specified hygiene requirements can be fulfilled. In order to suspend the support arm on the ceiling of the particular treatment room or operating theatre, a fixing device is required, which, where possible, enables the support arm to be pivoted horizontally so that, if necessary, in conjunction with the adjustment possibilities afforded by the support arm, it is possible to effect a relative change in the orientation and position of the medical apparatus in the treatment room or operating theatre.
A fixing device of this type is provided for example by the fixing device disclosed in DE 298 18 108 U1, which has the generic features of claim 1. The known fixing device has a base body, which may be fixed to the ceiling by a connecting element, for example by means of screwed inserts, arranged on a connecting portion of the base body. Provided alongside the base body, there are two mutually opposing bearing journals which are open towards the top, i.e. in the direction of the ceiling, and which are connected towards the bottom, i.e. in the direction of gravity, to bearing plates. It is possible to push a bearing sleeve of a support arm onto each bearing journal, the bearing sleeve being supported against gravity by the bearing plates. Part of the base body of the fixing device is arranged between the two bearing journals.
The fixing device known from DE 298 18 108 U1 has several disadvantages. Since the bearing journals are arranged alongside the base body, the rotatability of a support arm fixed on the bearing journal by means of its bearing sleeve is substantially restricted, since the support arm strikes the base body of the fixing device after a certain degree of rotation. Moreover, the rotatability of the support arm is further impaired since the two bearing journals lie opposite one another and thus the rotation of the support arm is impaired by the support arm fixed on the other bearing journal.
A further disadvantage of the known fixing device is that, as a result of the fact that the bearing journal is arranged alongside the base body, the bearing-journal axis, which defines the axis of rotation of the support arm, is spaced from the centre axis of the base body, producing a lever arm as a result of the spacing. Consequently, the weight-induced force of the spring arm and the apparatus fixed thereto, which acts on the bearing journal, generates a torque acting on the fixing device, so that, in addition to the weight-induced load, an additional torque-induced load has to be taken up by the fixing device and the connection between the fixing device and the said ceiling.
Moreover, in the case of the known fixing device, in the event of anxe2x80x94in particular jolt-likexe2x80x94raising of the support arm for the purpose of changing for example the vertical position of an apparatus, there is a risk of the bearing sleeve of the support arm springing out of the bearing journal, which can result in considerable human injury and damage to equipment.
Therefore, the object of the invention is to provide a fixing device which enables a support arm fixed thereto to rotate in a desired manner, in particular any manner, whilst preventing an unnecessary load on the fixing device and taking into account the stringent safety requirements.
The object is achieved by a subject-matter having the features of claim 1. Advantageous further developments of the invention are possible as a result of the measures described in the subclaims.
The fixing device according to the invention has the advantage that the support arm fixed to the bearing portion of the base body by means of the bearing sleeve is capable of rotating in any manner, since the bearing portion is arranged in the axial direction at the lower end of the base body and projects axially beyond the remaining base body, so that the fixed spring arm is not impeded by the base body during pivoting. Moreover, the bearing sleeve of the support arm is held on the bearing portion by means of a retaining ring which may be fixed to the bearing portion, so that the bearing sleeve of the support arm is secured by the retaining ring and can only be removed once the retaining ring is released from the fixing device. The bearing portion is furthermore arranged in the axial direction at the lower end of the base body, so that a weight-induced force acting on the bearing sleeve fixed to the bearing portion produces at least substantially no additional torque which acts on the fixing device.
In advantageous manner, a first bearing element is provided which at least partially surrounds the bearing portion of the base body and at least partially abuts against the retaining ring, the bearing sleeve being supported on the retaining ring by means of the first bearing element. The first bearing element and the retaining ring form a first bearing in which the bearing sleeve of the support arm is supported.
Here, support is provided at least in the axial direction of the base body, i.e. in the direction of gravity, in order to ensure the rotatability of the support arm even under a heavy load, produced for example when a heavy apparatus is fixed to the support arm. It is possible for the first bearing formed by the first bearing element to also provide radial support, particularly when high torque-induced forces acting on the bearing sleeve are expected.
It is furthermore advantageous that a second bearing element is provided, which at least partially surrounds the bearing portion of the base body and forms a second bearing for supporting the bearing sleeve, said second bearing lying opposite the first bearing formed by the first bearing element. Thus, the bearing sleeve is supported on both sides, ensuring particularly good rotatability of the support arms.
In advantageous manner, the second bearing element of the second bearing is constructed in the form of a sleeve, radial support being provided by the second bearing. It is furthermore advantageous that the first bearing element of the first bearing is constructed in the form of a circular ring, axial support being provided by the first bearing. Since, owing to the geometrical arrangement, the weight-induced force of the support arm acts substantially on the first bearing, whilst any torque produced acts almost exclusively on the second bearing, the spring arm is thus supported in a manner which is adapted to the load. For the purpose of taking up any torque produced, it is nevertheless advantageous that the second bearing also provides axial support and/or the first bearing also provides radial support.
In advantageous manner, the retaining ring may be fixed to the bearing portion of the base body by at least one retaining screw. Here, the retaining screw can engage in a threaded bore constructed in the bearing portion of the base body, or in a groove constructed in the bearing portion of the base body. The retaining screw can nevertheless be applied against the surface of the bearing portion of the base body with an arresting force for the purpose of generating a static friction force for fixing the retaining ring. In any case, the retaining screw provides numerous fixing possibilities, which can be realised in constructively simple manner.
It is advantageous that the external diameter of the retaining ring corresponds at least approximately to the external diameter of the bearing sleeve of the support arm to be fixed. Thus, the reliability of the retention of the bearing sleeve of the support arm is improved by means of the retaining ring fixed to the bearing portion of the base body, since, for geometrical reasons, mechanical influence, for example due to a cable hanging down, is prevented from affecting the retaining ring.
It is advantageous that the base body is constructed at least substantially in the form of a tube, since this enables a compact construction of the fixing device to be achieved.
It is advantageous that the fixing device has a securing means which may be fixed to the connecting portion of the base body for the purpose of securing a connection which is formed by the connecting portion for the purpose of suspending the fixing device. Here, the fixing device can be fixed to the ceiling of the treatment room or operating theatre for example by means of a connecting portion. If the connection becomes loose, for example as a result of an excess load or an accident, then the securing means supports the drop of the fixing device and thus at least partially the suspension of the support arm.
In advantageous manner, a plurality of bearing portions are provided for fixing a plurality of support arms, which are arranged successively in the axial direction of the base body, each of the bearing sleeves of the support arms abutting against at least one retaining ring for the purpose of support. It is thus possible for a plurality of support arms to be fixed to the fixing device in rotatably supported manner. As a result of the successive arrangement of the respective bearing portions in the axial direction of the base body, each of the support arms is able to rotate fully, without the rotatability of one support arm being influenced by the other support arms.
It is advantageous that the fixing device has a bearing journal arranged alongside the base body, it being possible to push a bearing sleeve of a support arm onto said bearing journal. It is thus possible to use the space available alongside the base body to fix a support arm for which total rotatability is not required.